Studies on the interaction between tetraphenylporphyrin compounds and bovine serum albumin.

The interaction of three porphyrin compounds with bovine serum albumin (BSA) was examined by fluorescence emission spectra at the excitation wavelength 280 nm and in UV-Vis absorption spectra. Through fluorescence quenching experiments, it was confirmed that the combination of three porphyrin compounds with BSA was a single static quenching process. The binding constant K(A), the thermodynamic parameters enthalpy change (DeltaH(0)), Gibbs free energy change (DeltaG(0)) and entropy change (DeltaS(0)) were obtained. It was found that hydrophobic interaction played a main role in tetraphenylporphyrin (TPP) or tetraparacholophenylporphyrin (TClPP) binding to BSA, while tetraparamethoxyphenylporphyrin (TMEOPP) mainly based on van der Waals' force. According to F?ster energy transfer, the separate distance r, the energy transfer efficiency E and F?ster radium R(0) were calculated. The results obtained from the above experiments showed that three porphyrin compounds were tightly bound to BSA.